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Manufacture of dihydroxy aromatic compounds by alcoholysis of polycarbonate-containing compositions

a technology of alcoholysis and polycarbonate, which is applied in the preparation of organic carbonates, organic compound preparations, organic chemistry, etc., can solve the problems of difficult depolymerization of polycarbonates in wastes, significant bulk waste disposal problems, and inability to biodegrade polycarbonates, etc., to achieve the effect of reducing the color of crude dihydroxy aromatic compounds

Inactive Publication Date: 2014-03-25
SAUDI BASIC IND CORP SA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent text describes how using a titanium-based catalyst can lead to the formation of yellow-colored dihydroxy aromatic compounds during the depolymerization of polycarbonates. However, the inventors found that these compounds can be converted to a white color by adding an acid or a base in the presence of a solvent. This conversion is believed to be caused by the breakdown of the colored complex formed between the dihydroxy aromatic compound and the titanium-based catalyst. The technical effect of this invention is the ability to obtain a high-quality, white dihydroxy aromatic compound.

Problems solved by technology

However, polycarbonates are not biodegradable and can present a significant bulk waste disposal problem.
However, it is challenging to depolymerize polycarbonates in wastes, particularly, post-consumer low purity wastes, since these wastes contain various chemicals in addition to polycarbonates.
These various chemicals can poison the catalyst, contaminate the products, and render the process expensive and inefficient.

Method used

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  • Manufacture of dihydroxy aromatic compounds by alcoholysis of polycarbonate-containing compositions
  • Manufacture of dihydroxy aromatic compounds by alcoholysis of polycarbonate-containing compositions
  • Manufacture of dihydroxy aromatic compounds by alcoholysis of polycarbonate-containing compositions

Examples

Experimental program
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Effect test

example 1

[0072]43 g of standard BPA was dissolved in 300 ml of methanol to form a clear solution. After 0.2 g of Ti-isopropoxide catalyst was added the solution turned yellow. The solution had an APHA value of 2112 (sample A). A 100 ml sample of this yellow solution was taken, and 50 ml of 15% NaOH solution was added at room temperature. There was a reduction in the yellow color of the solution. The solution was neutralized with 50% HCl solution until the precipitation of BPA was complete. The APHA of the obtained BPA was measured to be 612.

example 2

[0073]43 g of standard BPA was dissolved in 300 ml of methanol to form a clear solution. Then 0.2 g of Ti-isopropoxide catalyst was added to the solution. The solution turned yellow. A 100 ml sample of this yellow solution was taken, and 50 ml of 5% HCl solution was added and heated for 30 min at 100° C. The solution turned colorless, and the mixture was brought to room temperature. Water was added until precipitation was complete. The precipitated BPA was filtered. The APHA value of the obtained BPA was measured to be 56. Prior to acid treatment, the BPA sample (sample A) had an APHA of 2112.

examples 3-14

[0074]A series of experiments were carried out to reduce the color of crude BPA obtained from methanolysis of polycarbonate-containing compositions. The color values of the samples on the American Public Health Association color index (referred to as “APHA values”) are listed in Table 2. These experiments showed that BPA purity could be improved by toluene crystallization in the presence of an acid. Recrystallization of crude BPA with toluene enhances the purity from 79% to 99.7%. The results of various acids on the color by toluene crystallization have been tabulated along with the APHA value on Table 2.

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Abstract

A method to produce a purified dihydroxy aromatic compound from a polycarbonate-containing composition is provided. The method includes depolymerizing the polycarbonate by alcoholysis using a titanium-based catalyst producing a dihydroxy aromatic compound and a dialkyl carbonate, recovering the dihydroxy aromatic compound as a crude dihydroxy aromatic compound; and contacting the recovered crude dihydroxyl aromatic compound with an acid in the presence of a solvent at an elevated temperature. Alternatively, the method comprises dissolving the recovered crude dihydroxyl aromatic compound in a solvent; contacting the dissolved crude dihydroxy aromatic compound with a base; and neutralizing the combination of the dissolved crude dihydroxy aromatic compound and the base with an acid.

Description

BACKGROUND[0001]This disclosure is directed to methods for the manufacture of dihydroxy aromatic compounds by alcoholysis of polycarbonate-containing compositions, and in particular to methods of making bisphenol A by methanolysis of bisphenol A polycarbonate-containing compositions.[0002]Polycarbonates are useful in the manufacture of articles and components for a wide range of applications, from automotive parts to electronic appliances. However, polycarbonates are not biodegradable and can present a significant bulk waste disposal problem. Accordingly, efforts have been made to recover valuable resources from polycarbonate wastes.[0003]Polycarbonates can depolymerize in the presence of a catalyst to generate monomers such as bisphenol A and dimethyl carbonate. However, it is challenging to depolymerize polycarbonates in wastes, particularly, post-consumer low purity wastes, since these wastes contain various chemicals in addition to polycarbonates. These various chemicals can poi...

Claims

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Application Information

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IPC IPC(8): C08G64/00C08G63/02
CPCC08G64/42C08J11/24C08J11/26C08G64/16C07C37/0555C07C37/84C07C68/06C08J2369/00Y02W30/706Y02W30/62C07C39/16C07C69/96
Inventor BELL, PHILIP WESLEYSTANISLAUS, ALEXANDERGANAPATHY BHOTLA, VENKATA RAMANARAYANAGUNALE, TUKARAMJAYANNA, DARSHAN
Owner SAUDI BASIC IND CORP SA
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